In an electric vehicle, a fuel cell powered vehicle, a hybrid car, etc., it is possible to use an electric motor as a power source for running a vehicle, and from the point of high design freedom of the electric motor for being mounted on the vehicle, freedom for designing a vehicle body is greatly increased. Therefore, the freedom in shape or structure of a structural body for a vehicle interior is also increased greatly. Further, such a vehicle capable of using an electric motor as a power source for running the vehicle is little in exhaust of carbon dioxide synthetically, and is paid attention to as a global environment adaptable-type vehicle. In particular, recently, a concept of LCA (Life Cycle Assessment) is also taken into consideration, and reduction of the amount of exhaust of carbon dioxide all over the life of a vehicle including its material from the stage of manufacture of the vehicle, through the term of use of the vehicle, up to scrapping of the vehicle, is being estimated.
On the other hand, for a vehicle, as fundamentally required specifications, a structure for ensuring safety of a passenger at the time of collision and the like, lightening in weight of a vehicle body for improving fuel consumption and the like, and excellent mass productivity and reduction in cost for manufacture, etc. are required. As a structure for improving safety of a passenger, for example, a design concept is paid attention to wherein it is preferred to employ a rigid structure capable of suppressing a deformation as little as possible for a vehicle interior which is a space for residence of a passenger, and to employ a soft structure (also called as a crushable structure) for absorbing an impact from outside at the time of collision (collision at front side and collision at rear side, etc.) and the like effectively and suppressing influence to the vehicle interior as little as possible for vehicle front part or rear part connected to a vehicle interior structure part. Further, in order to ensure safety of a passenger, also required is a design for suppressing influence due to an impact load from outside, at the time of rolling over and the like, to a vehicle interior as little as possible.
As a structure for ensuring safety of a passenger at the time of collision and the like including lightening in weight of a vehicle body, for example, a structure is proposed wherein a vehicle body structural part is formed by a fiber-reinforced resin (for example, Patent document 1). In this structure disclosed in Patent document 1, a vehicle body structural part forming a lower part of a vehicle body and a vehicle interior part are formed independently from each other, and the vehicle body structural part is formed by a fiber-reinforced composite material to give an impact energy absorbing function thereto.
In this structure disclosed in Patent document 1, however, because the vehicle body structural part and the vehicle interior part are formed independently from each other, there is a limit in the productivity, particularly in the mass productivity. Therefore, it is not a structure remarkably advantageous for reducing the cost for manufacture. Further, although a device on structure for absorbing an impact energy is added for the vehicle body structural part positioned at a lower part of the vehicle interior part, a device for improving safety of a passenger, such as a rigid structure capable of suppressing deformation as little as possible, is not taken care of for the vehicle interior part. Namely, although the care for ensuring the safety by absorbing an impact energy by the vehicle body structural part is taken for a passenger in the vehicle interior, the structure is not considered to be a structure taken care of sufficiently from the viewpoint of ensuring safety of a passenger by suppressing deformation of the vehicle interior or suppressing transmission of a load into the vehicle interior from outside. Further, if a vehicle interior structural part is attempted to be reinforced in a usual metal vehicle body, it takes much time for assembly of reinforcement parts or bonding due to welding and the like, and a continuity due to molding such as that in a fiber-reinforced resin cannot be expected, and therefore, lightening in weight is difficult.